Field of the Invention
The present invention relates to an upper electrode, a table (or lower electrode), a plasma processing apparatus including at least one of the upper electrode and table, a plasma processing method and a storage medium, each used for processing a substrate to be processed, such as a semiconductor wafer or the like, to which a plasma process is provided.
Background Art
In a step for manufacturing semiconductor devices, for example, a dry etching process, an aching process and the like has been known, as the plasma process for processing the substrate by changing a processing gas into plasma. In an etching apparatus for performing the dry etching process, for example, a pair of parallel and flat electrodes are vertically arranged to be opposed to each other. By application of high frequency electric power to a space between the two electrodes, the processing gas introduced into the space can be changed into the plasma. As a result, the substrate to be processed, such as the semiconductor wafer (hereinafter referred to as “the wafer”) or the like, which is placed on the lower electrode, can be subjected to the etching process. For example, as the etching process, a process for forming recesses in a film formed on the wafer, by using a resist pattern, as a mask, provided on the film to be etched, has been known.
In recent years, a “lower energy and higher density” process, requiring lower ion energy in the plasma and higher electron density, has been widely used in the plasma process. For instance, in the case of etching a silicon film or any other organic film, properly high frequency electric power is generally applied to the electrode provided on a lower side, in order to generate higher density plasma and suppress introduction or capture of ions into the wafer.
In some cases, for the generation of such lower energy and higher density plasma, an extremely high frequency, e.g., 100 MHz, of the high frequency electric power should be required, as compared with the frequency (e.g., approximately several ten MHz) that has been employed so far. However, such an extremely high frequency of the electric power applied to the apparatus may tend to considerably increase intensity of an electric field around a central portion of a surface of the electrode, i.e., a region corresponding to a central portion of the wafer, while relatively decreasing the intensity of the electric field around the periphery of the wafer. Therefore, as shown in FIG. 16, the etching process is progressed at a higher rate around the central portion of the wafer, while exhibiting a significantly lower etching rate around the periphery of the wafer.
To address such problems, Patent Documents 1 and 2 disclose improved etching apparatuses, respectively. Each of these apparatuses is intended for enhancing in-plane uniformity of the plasma process, by embedding a dielectric in a region around the central portion of the upper electrode, such that distribution of the electric field can made uniform by the dielectric. In fact, such an etching apparatus is suitable for providing the plasma process to each wafer having the same layered structure under the same conditions. In some cases, however, the etching process should be provided to different wafers, such as those having different films to be etched and/or different kinds of resist pattern films formed thereon. Additionally, although having the same layered structure, each wafer sometimes has the resist pattern formed thereon with a different shape and/or is sometimes designed to have the recesses each formed in the film while having a different aspect ratio (i.e., a ratio of a depth of the recess relative to a diameter of an opening thereof).
In such a case, the process conditions, such as a kind and/or pressure of each processing gas used, each value of the high frequency electric power and the like, should be controlled, corresponding to a kind or the like of each wafer. Therefore, the state or condition of the plasma should also be changed with such control of the process conditions. Thus, for enhancing the in-plane uniformity of the plasma process, it is necessary to control the distribution of the electric field, corresponding to the process conditions. However, in the etching apparatus having the dielectric provided in the upper electrode as disclosed in the above Patent Documents, the dielectric should be exchanged with another one, such as by disassembling the apparatus, in order to control the distribution of the electric field. This makes it substantially difficult to optionally control the distribution of the electric field, corresponding to the process conditions.
Patent Document 3 describes a technique for controlling a relative permittivity, by providing a control part formed from a dielectric material, between a chamber body and a first electrode. More specifically, the control part has a tank-like structure provided therein, such that a material that can optionally control the relative permittivity can be supplied into the tank-like structure. This configuration is only aimed to control the equivalent relative permittivity, by controlling a degree of electrical connection between the first electrode and the grounded chamber body. Accordingly, this technique cannot solve the above problems in nature.
Patent Document 1: JP2000-323456A (Paragraph [0049], FIG. 4)
Patent Document 2: JP2005-228973A (Paragraphs [0030] to [0033], FIG. 1)
Patent Document 3: JP2007-48748A (Paragraph [0038], FIGS. 3 to 5)